This is the hardest part: remember to soak your cashews in a large bowl on the counter overnight approximately 24 hours before you plan to make the mayonnaise.
If you forget to soak the cashews, no worries. Just add them to a saucepot and cover with 2 inches of water. Bring to a boil. When the water is at a rolling boil, remove from heat and let sit on the counter for about 15-30 minutes. Add about 1/4 of water to the mayonnaise recipe if you go this route.
Add all ingredients to a high-powered food processor or blender. Run for about 3-4 minutes, stopping as needed to scrape down the sides.
Transfer to glass container and store in the fridge.